An advertisement states that $4$ out of $7$ dentists recommend Minty Fresh Mouthwash. If $1421$ dentists were surveyed, how many dentists recommended Minty Fresh Mouthwash?
Explanation: If $1421$ dentists were surveyed, then $\frac{4}{7}\times1421=\boxed{812}$ of them recommended Minty Fresh Mouthwash.